The present invention relates generally to integrated circuits, and more particularly to operational amplifier circuits.
It is often desirable in today's rapidly changing semiconductor technology to design for circuit operability over a wide range of power supplies. Reduced power consumption with low power supplies may be particularly desirable for many applications. To decrease research, development, and manufacturing costs, single chip solutions for both high and low supplies are often targeted when developing various system elements. However, low supply voltage levels may have detrimental effect on analog component operational characteristics.
Particularly, operational amplifiers may perform poorly in environments providing low supply voltage levels. For example, analog transistors in the operational amplifier may manifest poor performance characteristics at low level operational voltages. Consistency in transconductance characteristics across the full range of input voltages is often sacrificed in the low voltage operational environment.
It may be desirable to have an operational amplifier capable of operating in a low voltage environment that would retain essential operational characteristics, for example, those derived from certain input analog transistors. It may also be desirable to have an operational amplifier capable of maintaining substantially constant transconductance characteristics across a full range of input voltage levels while maintaining a high level of input impedance. Additionally, it may be desirable to provide an operational amplifier capable of avoiding dead band behavior commonly found in “rail-to-rail” input stages.